Production of cracking feed stocks



United States Patent PRODUCTION OF CRACKING FEED STOCKS Robert J.Convery, Wilmington, DeL, Junior West Loveland, Swarthmore, Pa., andWayland E. Noland, Minneapolrs, Minn, assignors to Sun Oil Company,Philadelphla, Pa., a corporation of New Jersey Filed Sept. 28, 1962,Ser. No. 226,998 1 Claim. (Cl. 208-247) This application is acontinuation-in-part of application Senial Number 214,128 filed August1, 1962.

This invention relates to the production of cracking feed stocks. Morespecifically the invention is directed to a process for treating wholeor reduced asphalt base crude petroleum oils to obtain high grade feedstocks for cracking, particularly catalytic cracking.

Numerous processes have been suggested for the upgrading of asphalticcrude oils to condition them for cracking. These oils contain relativelylarge amounts of sulfur, nitrogen and metals including vanadium, nickeland iron. In addition, asphaltic oils form coke under crackingconditions which reduces the activity of crack ing catalysts. Coke isalso a detriment in thermal cracking because it plugs process units andtransfer lines. Such processes as solvent extraction, hydrogenation andtreatment with acids and solid adsorbents have been used in the past toprepare heavy oils for cracking. All of these processes havedisadvantages and limitations, one of these being high cost.

The present invention is based on the discovery that asphaltic oils canbe prepared for cracking by treatment with zinc chloride in a processwhich yields valuable by-products thus lowering treating costs. Incopending application Serial Number 214,128, filed August 1, 1962, thereis described a process for converting heavy petroleum fractions into aunique spectrum of products by treatment with zinc chloride. We havefound that coke formers, sulfur, nitrogen and metals can be removed fromwhole or reduced asphaltic crude oils employing zinc chloride to providea high quality thermal or catalytic cracking stock. The process isparticularly applicable to the preparation of stocks for catalyticcracking because of the sensitivity of the catalysts to coke, sulfur,nitrogen and metals.

Suitable feeds for the process are asphaltic petroleum fractions havinginitial boiling points ranging from 200- 700 F. These oils contain from10-50 vol. percent asphaltic components and have an A.P.I. gravityranging from 0.0 to 30 and a viscosity of from 10 to 2200 seconds (SUS)at 210 F. The feeds can be whole crude or crudes reduced by topping,vacuum distillation, visbreaking or solvent deasphalting. High sulfurand metals content are common in West Texas, Mexican and Venezuelancrudes. The feed can be blended with cutter stock, cycle oil fromcracking, recycle from the zinc chloride treating step, or otherrefinery streams.

The feeds can contain from 0 to 10 wt. percent sulfur, from 0 to 5 wt.percent nitrogen and from 0 to 2 wt. percent (0 2000 ppm.) metals. Thechief metal contaminant is vanadium and it is usually present in amountsranging from 0.0 to 1.0 wt. percent. Metals are usually present in theform of organometallic compounds.

The zinc chloride treating step is described in the above mentionedcopending application. The oil and zinc chloride are treated in anysuitable reactor with heating to maintain a temperature in the range offrom about 220 to about 500 C. and with agitation. No special type ofcontacting equipment is required. Batch or continuous operation can beused.

Zinc chloride can be added as a powder, a semi-solid mass or a solutionin water, alcohols, ethers, aldehydes or other suitable solvents sinceit is not easily obtained 1n anhydrous form it will usually contain atleast 5% water. Technical or crude grades of zinc chloride givesatisfactory results. Amounts ranging from .1 to 200 wt. percent or more(based on the oil feed) can be used, with amounts ranging from 1 wt.percent to 50 wt. percent being preferred. In one embodiment the zincchloride is activated with pyridine or other organic nitrogen base. Theaction of zinc chloride is at least partly catalytic.

Temperature control is critical. The treating is carried out attemperatures between about 220 C. and 500 C. with a temperature range of250 C. to 450 C. being preferred. The optimum temperature range is300-400" C. It is important to note that materials such as aluminumchloride and ferric chloride cannot be used at temperatures within thisrange because they sublime and distill under practical operatingtemperatures.

Temperatures above 450 C. cause considerable cracking of the oil whichis not the desired reaction and for this reason it is preferable tooperate below 450 C. Very little reaction occurs below 220 C.

Pressure is not critical and for reasons of convenience atmospheric orambient pressure is preferred. Pressures ranging from 5 p.s.i.a. to 500p.s.i.a. are suitable. Reaction times can vary from 10 minutes to 50hours depending in part on the temperature and on the type and amount offeed. One skilled in the art can coordinate the conditions to arrive atoptimum yields.

The zinc chloride treating step produces a gas-vapor fraction, a liquidfraction and a solid fraction. The gasvapor fraction contains from about1.0 to about 3.0 wt. percent hydrogen and a C C fraction. The liquidfraction comprises from 40-70 wt. percent of an oil having a low sulfur,nitrogen and metals content which is an excellent stock for catalyticcracking. The solid product of the zinc chloride treating steprepresents from about 15-40 wt. percent of the original feed. Itcontains a major proportion of a material which we call asphalt blackand may or may not contain small amounts of asphaltenes. Coke formers,sulfur, nitrogen and metals are concentrated in the solid product.

The asphalt black product produced by the zinc chloride treating step isunique. Most solid products resulting from treatments of heavy asphalticmaterials are soluble in the common hydrocarbon solvents. Asphalt blackis not soluble in hexane, benzene or CCl The X-ray diffraction patternhas a between plane spacing of 3.383.43 Angstroms. Asphalt black has asurface area ranging from about 65 to about square meters per gram. Itis infusible below 500 C. The hydrogen to carbon molecular ratio rangesbetween .35 and 0.80. One sample had the following partial analysis:75.15% carbon; 3.37% hydrogen; 12.03% oxygen; 0.47% nitrogen; 2.41%sulfur.

It can be used as a coloring agent, adsorbent, polymer filler and as acomponent of agricultural mulches, coatings and carbon electrodes.

The process of the invention is illustrated by the drawing which shows apreferred embodiment not intended to limit the disclosure.

An asphaltic oil contaminated with coke formers, sulfur, nitrogen andmetals containing compounds is fed through line 1 to a reaction zone 2.As previously stated the feed can be augmented or modified with recycleor additional feed components to adjust feed composition and properties.The latter materials are blended with the feed by means of appropriatelyplaced input lines, not shown. ZnCl is fed to the reactor through line3. The reactor is preferably maintained at a temperature of 300- 400 C.Inert gas such as nitrogen, helium, argon, etc. can be swept through thereactor through line 4 to maintain the reactants in a relatively oxygenfree atmosphere. This can be done by sweeping the inert gas through thereactor before the reactants are introduced if desired. As the reactionprogresses a gas-vapor stream containing hydrogen and C C hydrocarbonsis flashed off through line 5. This gas-vapor fraction usually comprisesabout 5-l0 wt. percent of the reaction products. It contains from about1 to about 3 wt. percent high purity hydrogen. A C fraction is recoveredthrough line 6 after cooling the gas-vapor fraction in heat exchanger 7and phase separation in separator 8. Hydrogen and C -C hydro carbons arerecovered as overhead through line 9. These gases are subsequentlyseparated into hydrogen and hydrocarbon components in any desired mannerwith conventional gas separating techniques and equipment, not shown.The liquid and solid reaction products, still mixed with zinc chloride,are removed from reaction zone 2 by line 10 and passed through coolingunit 11 wherein the product stream is cooled to a temperature of about50 C. The liquid and solid reaction products are then contacted with asolvent from line 12 in extractor 13. Extraction temperatures rangingfrom 0 to 400 C. can be used. Suitable solvents include non-polarsolvents such as low molecular weight hydrocarbons containing 3-10carbon atoms, i.e., propane, pentane, hexane, naphtha, benzene, toluene,xylene or other solvents like acetone, CCl etc. The extract is passed byline 14 to solvent recovery zone 15. Solvent is recovered in zone 15 andpreferably recycled by means not shown. The improved cracking feedsubstantially decreased in coke formers, sulfur, nitrogen and metals isthen passed by line 16 to a conventional cracking system 17. Aspreviously stated the cracking can be thermal or catalytic or acombination process.

The solid product from extractor 13 which we term asphalt black isinsoluble in propane, pentane, naphtha, benzene and carbontetrachloride. It is to be understood that the use of solvent extractionfor separation of the asphalt black from the liquid product isnon-limiting and other separation techniques such as filtration,centrifuging, adsorption, etc., can be employed in conjunction with orinstead of solvent extraction.

The asphalt black is fed by line 18 to desulfurization zone 19. Asolution of 5% HCl in methanol is fed by line 20 into thedesulfurization zone. The HCl converts ZnS (made in the reaction zone 2)to ZnCl with the subsequent release of H S. The sulfur recovered fromthe H 8 amounts to about 0.5 wt. percent of the feed. Thedesulfurization treatment can be omitted if desired. The solids are thenpassed by line 21 to a filter 22. The material is heated to about 65 C.to solubilize the ZnCl prior to or during filtration. The ZnCl isdischarged by line 23 to a recovery zone 24 and the asphalt black isrecovered through line 25. The zinc chloride can be recovered from themethanol by crystallization, spray drying or by distillation. The ZnClis recycled through line 25. The asphalt black can be treated to recovermetals if desired.

The liquid product is passed to a thermal, catalytic or combinationcracking operation. Any conventional type of cracking can be employed.

Suitable types of catalytic cracking are the fluidized bed, fixed bedand moving bed types. Catalysts can be oxides of metals of groups II,III, IV and V of the Periodic Table.

Major process variables such as temperatures, pressure, catalyst to oilratio and space velocity for the various types of cracking are wellknown to those skilled in the art.

The features of the various types of cracking which may be used in thecracking step of this invention are dis-.

The following example shows the effect of the process on Boscan crudehaving the following properties:

Initial boiling point F 456 A.P.I. gravity at 60 F. 11.4 Pour test F +65Viscosity-Saybolt seconds-furol 1 At 180 F. 222 At 210 F.

1 1 sec. Saybolt furol-seconds is approximately equal to 10 sec. SUS

Elemental composition: Percent C 84.43 H 9.67 H/ C 1.3 6 O 1.26 N 0.90 S4.77

Metals: Percent Vanadium 0.67 Nickel Iron 0.53

406.5 grams of the feed was placed in a reactor at C. and atmosphericpressure and the reactor was swept with nitrogen, 102.0 grams ofcommercial reagent grade ZnCl was added in powder form. The mixture washeated with stirring and the initial reaction temperature was about250275 C. as evidenced by the evolution of hydrogen. The reactants weremaintained at a temperature of 320-360 C. for 23 hours. The gas andvapor products were continuously flashed off at about 320 C. and thehydrocarbons separated from hydrogen by collection in an air cooled trapfollowed by a Dry Ice cooled trap. In addition to hydrogen, the productsincluded ethane, propane, isobutane, n-butane, iso-pentane, n-pentane,hexanes, propylene, butylenes, pentenes, hexenes and aromatic ends. Thequantitative analysis was-H 1.3 wt. percent; C C 5.5 wt. percent; C C7.4 wt. percent.

The liquids and solids from the reactor were cooled to about 50 C. andwashed with 3-500 cc. volumes of n-hexane. 51.5 wt. percent hexanesolubles (based on the feed) were recovered. The fraction had an A.P.I.gravity at 60 F. of 21.6 and a viscosity at 210 F. of 4 Saybolt-secondsfurol. The sulfur content was 2.4 wt. percent as compared with 4.77 wt.percent in the crude feed. Metals content was drastically reduced, theamounts being vanadium .0006 wt. percent; nickel .0001 wt. percent andiron -.0003 wt. percent. This material is well suited for thermal orcatalytic cracking as the specifications indicate. By the way ofcomparison the hexane solubles of Boscan crude which has not beentreated with zinc chloride have the following properties: 4.67 wt.percent sulfur, viscosity at 210-9 Saybolt furol seconds and A.P.I.gravity at 60 F.l7.4. This indicates that mere solvent extraction of thecrude does not provide a satisfactory cracking stock.

An atmospheric bottoms sample of a Venezuelan crude oil having aninitial boiling point of 650 F. contained 2.69 Wt. percent sulfur. Aftertreatment with zinc chloride the hexane solubles contained only 1.06 wt.percent sulfur and the oil was satisfactory for cracking in the presenceof a sulfur sensitive catalyst.

Equivalent reductions in metals, coke formers, sulfur and nitrogen areobtained by treating other crude oils and reduced crudes in the zincchloride treating step of the invention.

The process of the present invention can be used in conjunction withother petroleum processing steps such as coking, propane deasphalting,furfural extraction, vacuum distillation, visbreaking,hydrodesulfurization, reforming the like.

We claim:

A process for producing a high quality catalytic cracking feed stockcomprising the steps of contacting an asphalt base crude petroleumfraction contaminated with coke formers, sulfur, nitrogen and metalswith zinc chloride at a temperature in the range of from 220 to 500 C.,said petroleum fraction having an initial boiling point ranging fromZOO-700 F., containing 10-50 vol. percent asphaltic components andhaving an A.P.I. gravity ranging from 0.0 to 30 and a viscosity of from10 to 2200 seeonds (SUS) at 210 F., and separating a gas-vapor fraction,an asphalt black fraction insoluble in benzene, and a liquid fraction,said liquid fraction being substantially decreased in coke formers,sulfur, nitrogen and metals and suitable for catalytic cracking.

References Cited by the Examiner UNITED STATES PATENTS 2,108,438 2/1938Kimball 208296 5 2,291,886 8/1942 Egloif 208296 2,945,803 7/1960 Beutheret al. 20889 2,970,105 l/1961 Condo et al. 208247 10 DELBERT E. GANTZ,Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

